1. Technical Field
The present disclosure relates generally to radio frequency (RF) signal circuitry, and more particularly to multiple band multiple mode transceiver front end flip-chip architectures with integrated power amplifiers.
2. Related Art
Wireless communications systems find applications in numerous contexts involving information transfer over long and short distances alike, and there exists a wide range of modalities suited to meet the particular needs of each. Chief amongst these systems with respect to popularity and deployment is the mobile or cellular phone, and it has been estimated that there are over 4.6 billion subscriptions worldwide.
Generally, wireless communications involve a radio frequency (RF) carrier signal that is variously modulated to represent data, and the modulation, transmission, receipt, and demodulation of the signal conform to a set of standards for coordination of the same. Many different mobile communication technologies or air interfaces exist, including GSM (Global System for Mobile Communications), EDGE (Enhanced Data rates for GSM Evolution), and UMTS (Universal Mobile Telecommunications System). Various generations of these technologies exist and are deployed in phases, with one common third generation (3G) UMTS-related modality referred to as UMTS-FDD (frequency division duplexing) being W-CDMA (Wideband Code Division Multiplexing). More recently, 4G (fourth generation) technologies such as LTE (Long Term Evolution), which is based on the earlier GSM and UMTS standards, are being deployed. Besides mobile communications modalities such as these, mobile phones also incorporate local area data networking modalities such as Wireless LAN (WLAN), WiFi, ZigBee, and so forth. Along these lines, last-mile wireless broadband access technologies such as WiMAX (Worldwide Interoperability for Microwave Access) are also being implemented. In earlier iterations, these communications modalities have transmitted and received signals on a single channel or frequency, though the standards and implementing devices are evolving to handle dual band multi-mode and multi-band multi-mode operations.
A fundamental component of mobile handsets, or any wireless communications system for that matter, is the transceiver, that is, the combined transmitter and receiver circuitry. The transceiver encodes the data to a baseband signal and modules it with an RF carrier signal. Upon receipt, the transceiver down-converts the RF signal, demodulates the baseband signal, and decodes the data represented by the baseband signal. An antenna connected to the transmitter converts the electrical signals to electromagnetic waves, and an antenna connected to the receiver converts the electromagnetic waves back to electrical signals.
Conventional mobile handset transceivers typically do not generate sufficient power or have sufficient sensitivity for reliable communications standing alone. Thus, additional conditioning of the RF signal is necessary. The circuitry between the transceiver and the antenna that provide this functionality is referred to as the front end circuit, which includes a power amplifier for increased transmission power, and/or a low noise amplifier for increased reception sensitivity, and antenna switch to switch among different modes such as transmit, receive, Bluetooth modes. Each band or operating frequency of the communications system has a dedicated power amplifier and low noise amplifier.
In order to alternatingly connect the single antenna to one transmit chain and to one receive chain, the front end circuit includes a transmit/receive switch, as well as a power detector to detect the transmitted power, which feeds back to transceiver chain to control gain blocks such as AGC or PGA. Thus, a conventional power amplifier has a transmit input port, an antenna/output port, a voltage supply port, a power detector output port, and various control ports and ground ports. Because mobile devices are powered by an on-board battery, front end circuits therefore also include a low dropout voltage regulator or a buck boost voltage regulator.
The complexity of the front end circuit is further increased for front end circuits of dual band and multi-band communications because of the aforementioned constituent components, and the corresponding input and output lines thereof that are multiplied for each band/operating frequency. This requires additional semiconductor die real estate, which results in increased production costs. Recently, the packaging of front end circuits and other semiconductor integrated devices are increasingly shifting away from quad flat no lead (QFN) to advanced flip chip technologies such as flip chip ball grid arrays (FCBGA), wafer level ball grid arrays (WLBGA) and wafer level chip scale packaging (WLCSP) to achieve the smallest possible footprint. The reduced sizes and available space attendant to such packaging modalities can present significant challenges, particularly in the design and implementation of RF front end circuit with multiple operating bands and multiple modes. In order to achieve the optimal performance in RF circuit, physical architecture is a critical consideration, as ground current and RF signal path flow affect the isolation, stability, and other performance parameters such as linearity, noise figure, and rejection levels of harmonics and other unwanted signal components. Accordingly, there is a need in the art for improved multiple band transceiver front end flip-chip architectures with integrated power amplifiers.